Two-part base construction for incandescent lamps is known such as disclosed in U.S. Pat. No. 3,852,631, assigned to the assignee of the present invention. In said prior art base constructions, the individual base parts have been formed in two half sections made of insulating material and which are joined together generally with external fastening means along the longitudinal lamp axis. While this type base construction facilitates ease of assembly during lamp manufacture, the length of the base parts formed in half sections often leads to physical distortion when these parts are manufactured as well as poor registration between the half sections during lamp manufacture.
The above indicated problems with two-part lamp base constructions are increasingly severe when the base is constructed with a ceramic material. More particularly, the firing of a ceramic material increases physical distortion so that controlling physical dimensions of a half section base part becomes increasingly difficult and which can lead to failure of the half sections to meet properly when joined together. The advantages of two-part base constructions are thereby largely lost when a ceramic material is required and which has resulted in use of a single base member requiring that a central cavity be machined in said member to physically support the vitreous lamp envelope.
It would be desirable to reduce difficulties still being experienced with two-part base constructions for incandescent lamps which are made of an electrically insulative material. It would be further desirable to form these base parts in a manner eliminating need for machining the aforementioned central cavity now customarily employed in the base member for this type of lamp as well as permit the base parts to be assembled together before final lamp manufacture. It would be further desirable to accomplish these objectives for this type lamp without undue modification or additional cost in either lamp or lamp base manufacture.